extern crate crossbeam_channel;
extern crate rustro;
extern crate sdl2;

use rustro::retro;
use rustro::retro::ffi::{GameGeometry, SystemAvInfo};
use rustro::retro::constants::{Input, DeviceIndex, JoypadButton, AnalogAxis};

use std::ffi::CStr;
use std::io::Read;
use std::path::{Path, PathBuf};
use std::pin::Pin;
use std::time::{Duration, Instant};

use structopt::StructOpt;

use sdl2::audio::{AudioCallback, AudioFormat, AudioSpec, AudioSpecDesired, AudioDevice};
use sdl2::controller::{GameController, Button, Axis};
use sdl2::event::Event;
use sdl2::keyboard::Keycode;
use sdl2::rect::Rect;
use sdl2::render::{TextureCreator, WindowCanvas};
use sdl2::video::WindowContext;

struct MyEmulator {
    retro: retro::wrapper::LibretroWrapper,
    av_info: SystemAvInfo,

    sdl_context: sdl2::Sdl,

    // video bits
    canvas: WindowCanvas,
    pixel_format: sdl2::pixels::PixelFormatEnum,
    texture_creator: TextureCreator<WindowContext>,

    // audio bits
    audio_buffer: Vec<i16>,
    audio_spec: AudioSpec,
    audio_device: AudioDevice<MySdlAudio>,
    audio_sender: crossbeam_channel::Sender<Vec<i16>>,

    // input bits
    gamepad_subsys: sdl2::GameControllerSubsystem,
    gamepads: Vec<GameController>,
}

impl MyEmulator {
    pub fn with_core(core: impl AsRef<Path>) -> Pin<Box<Self>> {
        let lib = libloading::Library::new(core.as_ref()).unwrap();
        let raw_retro = retro::loading::LibretroApi::from_library(lib).unwrap();
        let retro = retro::wrapper::LibretroWrapper::from(raw_retro);

        let title = format!(
            "{} - rust libretro",
            unsafe { CStr::from_ptr(retro.as_ref().get_system_info().library_name) }
                .to_string_lossy()
        );

        let mut av_info = retro.as_ref().get_system_av_info();
        let pixel_format = sdl2::pixels::PixelFormatEnum::ABGR1555;

        // HACK: some cores don't report this 'til we get an environ call to set_system_av_info...
        //  which is too late for this constructor to pass along to SDL.
        if av_info.timing.sample_rate == 0.0 {
            av_info.timing.sample_rate = 32040.0;
        }
        // similar hack, this one making sure we don't divide by zero in our frame limiter.
        if av_info.timing.fps == 0.0 {
            av_info.timing.fps = 60.0;
        }

        let sdl_context = sdl2::init().unwrap();

        let (width, height) = (av_info.geometry.base_width, av_info.geometry.base_height);

        let window = sdl_context
            .video()
            .unwrap()
            .window(title.as_str(), width, height)
            .opengl()
            .build()
            .unwrap();

        let canvas = window.into_canvas().build().unwrap();
        let texture_creator = canvas.texture_creator();

        let (audio_sender, audio_receiver) = crossbeam_channel::bounded(2);

        let audio = sdl_context.audio().unwrap();
        let desired_spec = AudioSpecDesired {
            freq: Some(av_info.timing.sample_rate.round() as i32),
            channels: Some(2),
            samples: None,
        };
        let mut audio_spec = None;
        let audio_device = audio
            .open_playback(None, &desired_spec, |spec| {
                if spec.format != AudioFormat::S16LSB {
                    println!("unsupported audio format {:?}", spec.format);
                }
                audio_spec = Some(spec.clone());
                MySdlAudio {
                    audio_spec: spec,
                    audio_receiver,
                }
            })
            .unwrap();

        let gamepad_subsys = sdl_context.game_controller().unwrap();
        let mut gamepads = Vec::new();
        for i in 0..gamepad_subsys.num_joysticks().unwrap() {
            gamepads.extend(gamepad_subsys.open(i).into_iter());
        }

        let emu = MyEmulator {
            retro,
            av_info,
            sdl_context,
            canvas,
            pixel_format,
            texture_creator,
            audio_buffer: Default::default(),
            audio_spec: audio_spec.unwrap(),
            audio_device,
            audio_sender,
            gamepad_subsys,
            gamepads,
        };
        let mut pin_emu = Box::pin(emu);
        retro::wrapper::set_handler(pin_emu.as_mut());
        pin_emu.retro.as_ref().init();
        pin_emu
    }

    pub fn run(&mut self) {
        self.audio_device.resume();
        let mut event_pump = self.sdl_context.event_pump().unwrap();
        'running: loop {
            let frame_begin = Instant::now();

            for event in event_pump.poll_iter() {
                match event {
                    Event::Quit { .. }
                    | Event::KeyDown {
                        keycode: Some(Keycode::Escape),
                        ..
                    } => break 'running,
                    _ => {}
                }
            }

            // The rest of the game loop goes here...
            self.retro.as_ref().run();
            self.canvas.present();

            Duration::from_secs_f64(1.0 / self.av_info.timing.fps)
                .checked_sub(frame_begin.elapsed())
                .map(std::thread::sleep);
        }
    }

    pub fn load_game(&self, rom: impl AsRef<Path>) {
        let mut data = None;
        let mut v = Vec::new();
        if let Ok(mut f) = std::fs::File::open(rom.as_ref()) {
            if f.read_to_end(&mut v).is_ok() {
                data = Some(v.as_ref());
            }
        }
        self.retro
            .as_ref()
            .load_game(Some(rom.as_ref()), data, None)
            .unwrap();
    }

    fn send_audio_samples(&mut self) {
        let stereo_samples = self.audio_spec.samples as usize * 2;
        while self.audio_buffer.len() >= stereo_samples {
            let remainder = self.audio_buffer.split_off(stereo_samples);
            let msg = std::mem::replace(&mut self.audio_buffer, remainder);
            let _ = self.audio_sender.try_send(msg);
        }
    }
}
impl retro::wrapper::Handler for MyEmulator {
    fn video_refresh(&mut self, data: &[u8], width: u32, height: u32, pitch: u32) {
        let rect = Rect::new(0, 0, width, height);

        if let Ok(mut tex) =
            self.texture_creator
                .create_texture_static(self.pixel_format, width, height)
        {
            if tex.update(rect, data, pitch as usize).is_ok() {
                self.canvas.clear();
                self.canvas.copy(&tex, None, None).unwrap();
            }
        }
    }

    fn audio_sample(&mut self, left: i16, right: i16) {
        self.audio_buffer.push(left);
        self.audio_buffer.push(right);
        self.send_audio_samples()
    }

    fn audio_sample_batch(&mut self, stereo_pcm: &[i16]) -> usize {
        self.audio_buffer.extend(stereo_pcm);
        self.send_audio_samples();
        stereo_pcm.len()
    }

    fn input_poll(&mut self) {
        self.gamepad_subsys.update();
    }

    fn input_state(&mut self, port: u32, device: Input, index: DeviceIndex) -> i16 {
        match self.gamepads.get(port as usize) {
            Some(gamepad) => {
                match device {
                    Input::Joypad(button) => {
                        match button_map(&button) {
                            Some(x) => gamepad.button(x) as i16,
                            None => match button {
                                JoypadButton::L2 => gamepad.axis(Axis::TriggerLeft),
                                JoypadButton::R2 => gamepad.axis(Axis::TriggerRight),
                                _ => 0,
                            }
                        }
                    }
                    Input::Analog(axis) => gamepad.axis(axis_map(index, axis)),
                    _ => 0,
                }
            }
            None => 0,
        }
    }

    fn get_can_dupe(&mut self) -> Option<bool> { Some(true) }

    fn set_pixel_format(&mut self, pix_fmt: retro::ffi::PixelFormat) -> bool {
        self.pixel_format = match pix_fmt {
            retro::ffi::PixelFormat::ARGB1555 => sdl2::pixels::PixelFormatEnum::RGB555,
            retro::ffi::PixelFormat::ARGB8888 => sdl2::pixels::PixelFormatEnum::ARGB8888,
            retro::ffi::PixelFormat::RGB565 => sdl2::pixels::PixelFormatEnum::RGB565,
        };
        true
    }

    fn set_system_av_info(&mut self, av_info: SystemAvInfo) -> bool {
        let (width, height) = (av_info.geometry.base_width, av_info.geometry.base_height);
        self.canvas.window_mut().set_size(width, height);
        self.canvas.set_logical_size(width, height);
        self.av_info = av_info;
        true
    }

    fn set_geometry(&mut self, geom: GameGeometry) -> bool {
        let (width, height) = (geom.base_width, geom.base_height);
        self.canvas.window_mut().set_size(width, height);
        self.canvas.set_logical_size(width, height);
        self.av_info.geometry = geom;
        true
    }
}


struct MySdlAudio {
    audio_spec: AudioSpec,
    audio_receiver: crossbeam_channel::Receiver<Vec<i16>>,
}

impl AudioCallback for MySdlAudio {
    type Channel = i16;

    fn callback(&mut self, out: &mut [Self::Channel]) {
        if self.audio_spec.format == AudioFormat::S16LSB {
            if let Ok(samples) = self.audio_receiver.recv() {
                out.copy_from_slice(&samples[..out.len()]);
            }
        }
    }
}

pub fn main() -> failure::Fallible<()> {
    let opt: Opt = Opt::from_args();
    let mut emu = MyEmulator::with_core(&opt.core);
    emu.load_game(&opt.rom);
    emu.run();

    Ok(())
}

#[derive(StructOpt)]
struct Opt {
    /// Core module to use.
    #[structopt(short, long, parse(from_os_str))]
    core: PathBuf,
    /// Rom to load using the core.
    #[structopt(short, long, parse(from_os_str))]
    rom: PathBuf,
}

fn button_map(retro_button: &JoypadButton) -> Option<Button> {
    match retro_button {
        JoypadButton::B => Some(Button::A),
        JoypadButton::Y => Some(Button::X),
        JoypadButton::Select => Some(Button::Back),
        JoypadButton::Start => Some(Button::Start),
        JoypadButton::Up => Some(Button::DPadUp),
        JoypadButton::Down => Some(Button::DPadDown),
        JoypadButton::Left => Some(Button::DPadLeft),
        JoypadButton::Right => Some(Button::DPadRight),
        JoypadButton::A => Some(Button::B),
        JoypadButton::X => Some(Button::Y),
        JoypadButton::L => Some(Button::LeftShoulder),
        JoypadButton::R => Some(Button::RightShoulder),
         // SDL2 controller API doesn't have L2/R2 as buttons, they're considered axes
        JoypadButton::L2 => None,
        JoypadButton::R2 => None,
        JoypadButton::L3 => Some(Button::LeftStick),
        JoypadButton::R3 => Some(Button::RightStick),
    }
}

fn axis_map(index: DeviceIndex, axis: AnalogAxis) -> Axis {
    match (index, axis) {
        (DeviceIndex::Left, AnalogAxis::X) => Axis::LeftX,
        (DeviceIndex::Left, AnalogAxis::Y) => Axis::LeftY,
        (DeviceIndex::Right, AnalogAxis::X) => Axis::RightX,
        (DeviceIndex::Right, AnalogAxis::Y) => Axis::RightY,
    }
}